Back spacing mechanism



Oct. 15. 1940. J. P. BARKDoLl.

I BACK SPACING MECHNISM Filed Feb. 18, 1939 2. Sheets-Sheet. 1

ATroRNEY A RSR F izf R5 Oct' 15 1940 J. P. BARKDQLI. 2,217,654

BACK SPACING MECHANISM Filed Feb. 18, '1939 2 sheets-sneer 2 ATTORNEY Patented Oct. 15, 1940 BACK SPAOING MECHANISM Joseph P. Barkdoll, Groton, N. Y., assignor to L. C. Smith & Corona Typewrlters, Inc., Syracuse, N. Y., a corporation of New York Application February 18, 1939, Serial No. 257,141

'l Claims. (Cl. 197-91l This invention relates to improvements in back spacing mechanism for back spacing the platen carriage of a typewriting machine.

The principal objects of the invention are to provide a back spacing mechanism which is positive and certain in its operation, will not overthrow when the back space key is quickly and violently operated, and is of a simple and light and inexpensive construction especially adapting ;o it for use in small portable typewriting machines.

To the foregoing ends, and other ends which will appear from the following description of a preferred embodiment of the invention illustrated in the accompanying drawings, the invention consists in the arrangements of parts, features of construction, and combinations of devices particularly pointed out in the appended'claims and hereinafter described.

In the drawings,

Fig. 1 is a fragmentary vertical longitudinal sectional view taken approximately midway the sides of the machine on the line I-I of Fig. 3;

Fig. 2 is a fragmentary vertical longitudinal sectional view on the line 2-2 of Fig. 3;

2.-, Fig. 3 is a fragmentary top plan view of the machine, certain parts being removed and others broken away for clarity of disclosure of the back spacing mechanism;

Figs. 4 and 5 are detail views similar to Fig. 3

illustrating the operation of the back spacing mechanism;

Fig. 6 is a detail sectional view on the line 6--6 of Fig. 4; and

Fig. '7 is a detail sectional view on the line 1-1 of Fig. 4.

The back spacing mechanism is illustrated as embodied in a small portable typewriting machine of the semi-front strike variety. Only so much of said machine as is necessary for a clear o understanding of the invention is shown and will be described.

In said machine the platen Ill is journaled as is common in the art in a. platen carriage II having the usual ball bearing mounting on a carriage bed I2, which is mounted on the main frame 2I of the machine. An upwardly and rearwardly inclined type bar segment 22 is mounted on the main frame. Said carriage is normally urged in letter feed direction from right to left by the :.0 usual spring drum and cable (not shown), and is controlled to feed step by step in letter feed direction by a known rotary escapement device. 'I'his device includes the dog rocker I3 rockable about an axis I38L and normally urged by its re- 55. turn spring I4 into a position in which the known spring-urged dog I6 pivoted on the rocker at I5s is yieldingly normally held by its spring Il" against a stop I5 on the rocker and is normally engaged by a tooth of the circular rack or escapement wheel I6 to hold the carriage against letter 5 feed advance. Said rocker is operable by a suitable universal bar (not shown) to disengage pivoted dog I5 from the wheel I6 and interpose the fixed or rigid dog I1 on said rocker in the path of travel of the wheel teeth in the known manner. 16 By this known type of rotary escapement the carriage is fed at the type strokes in the known manner step by step for letter spacing, there being provided the usual feed pinion I6, held to rotate in unison with the escapement wheel I6, 1I and the usual carriage-carried feed rack I9 meshing with pinion I8. The escapement wheel and feed pinion are journalled on a pivot mounting 20 to rotate about an upstanding axis located, as is usual, approximately midway the sides of the n machine. It will be obvious that the details of construction of the rotary escapement may be widely varied. The present invention relates to means for back spacing the wheel I6, and will now be described. g5

Adjacent the right hand side and rear of the machine, and mounted on a substantially vertical pivot 23 held to a bracket 24 which is ilxedly held to the carriage bed I2 by suitable fastening means, is a bellcrank lever 25 formed of sheet 30 metal. One arm of lever 25 extends in a general forward direction from pivot 23, and the other arm thereof extends in a general outward direction from pivot 23 toward the right hand side of main frame 2|. A rigid metallic wire link 26, 35 which extends substantially fore-and-aft of the machine adjacent the right hand side of the main frame, is pivotally connected at its rear end to the outer end of the said outwardly extending arm of bellcrank lever 25, said link having a hooklike rear end engaged in an aperture in said arm. Link 26 extends through a part of the main frame which is provided with a clearance aperture 43 for the link. Link 26 is pivotally connected at its forward end to the lower end of the lower arm of a sheet metal sub-lever 21 of the first order. said link having a hook-like forward end engaged in an aperture in said arm. Sublever 21 normally extends in a general upward and forward direction in the machine, and is fulcrumed on a pivot wire 28 to rock fore-and-aft of the machine about a horizontal axis extending transversely of the machine.

The upper arm of sub-lever 21 engages behind and over the downwardly and rearwardly extending arm of a sheet metal bellcrank back spacing key lever 29 which has a generally forwardly extending arm on which is ilxed the back space key 3U. The bellcrank back-spacing key lever 29 is fulcrumed on a pivot wire 3| to rock about a horizontal axis extending transversely of the machine, wire 3| being located above and forward of wire 28.

The two wires 29 and 3| cross a common guide slot 32 in a member 2|l of the main frame. Both the sub-lever and the key lever are engaged in and guided in this slot 32, the point of contact between the upper arm of the sub-lever and the pendent arm of the key lever being normally within the slot and the pendent key lever arm always remaining throughout its length in the slot.

The forwardly extending and key-carrying arm of the back spacing key lever 29 is normally yieldingly urged upward, by means hereinafter described, against the under side oi' a suitable key lever stop 33 fixedly held to the main frame 2|.

The foregoing described parts of the back spacing mechanism actuate a at sheet metal backspacing bar 34 which is disposed vertically edgewise thereof in the machine and extends inwardly from the forwardly extending arm of bellcrank toward the wheel I6 in a general direction transversely of the machine, said bar being directly engageable at its inner end with a tooth of wheel I6 to reversely rotate said wheel to back space the platen carriage when the back space key is depressed, all as more fully hereinafter described.

At its right hand end or outer end, the bar 34 is supported by, and is pivotally connected to, the forward end of the forwardly extending arm of bellcrank 25 for general endwise movement of the bar in a horizontal direction generally transversely of the machine upon vibration or rocking of bellcrank 25 on its pivot 23. For this purpose, in the construction shown, the forwardly extending arm of bellcrank 25 is formed with a hooklike forward end portion 25* which extends through an aperture (Fig. 6) formed in bar 34 closely adjacent the outer or right hand end of the bar, the open throat of said hook-like end portion of bellcrank 25 being directed toward the right hand side of the machine.

A back space mechanism return spring 36 is provided which normally returns the bar 34, bellcrank 25, link 26, sub-lever 21 and key lever 29 to, and yieldingly holds said parts in, the normal idle position of each said part shown in Figs. l, 2 and 3. 'This spring 36 is of the tension pull type and is anchored at its rear end to bracket 24 inward or to the left of pivot 23 of bellcrank 25, said spring extending inward and` forward to bar 34 from its anchorage to bracket 24 and being hooked at its forward end to bar 34 which is provided with an aperture 31 (Fig. 6) for this hooking of the spring to bar 34. Spring 36 exerts constantly both a rearward and a rightward pull on bar 34 at the point 31, thus constantly urging the bar endwise or longitudinally toward the right and also constantly tending to swing the bar facewise and horizontally rearward about its pivotal connection 35-2 5* to bellcrank 25.

Adjacent its left hand end or inner end, the bar 34 is slidably supported and guided for limited movement of the bar horizontally endwise or longitudinally and also for limited horizontal swinging movement of the bar facewise about its pivotal connection 35-25 to bellcrank 25`, with said bar in the plane of the wheel I6. The means shown for so supporting and guiding the bar 34 azuacent its inner end will now be described. A sheet metal bracket 33, rigidly fastened to the carriage bed I2 substantially midway the sides of the machine and extending forward from the bed, is formed adjacent its front end and slightly to the right of escapement wheel I6 with a ilat supporting, guiding and stop arm 39 for the bar 34. Arm 39 extends substantially horizontally fore-and-aft of themachine and is disposed edgewise of the arm in a vertical plane extending fore-and-aft of the machine, as shown. Intermediate its front and rear e'nds said arm 39 is cut away along its upper and lower edges to form a reduced supporting and guiding and stop portion 39* for bar 34, and to provide at the rear end of portion 39* a pair of stop shoulders 40 and at the front end of said portion 39a a pair of stop shoulders 4|. In the machine shown, the dog rocker I3 and the wheel I6 and pinion I8 of the rotary escapement device hereinbefore generally described are mounted on the bracket 38.

Adjacent its left hand end or inner end the bar 34 is formed with an elongated and closed horizontal slot 42 which extends longitudinally of the bar, is closed at both ends to provide end stop edges 42a and 42h, and has its inner end or stop edge 42 located close to the inner end of the bar, said slot being longer than the vertical depth of arm 39. Bar 34 may be easily assembled in the machine by passing its slotted end over the front end of arm 39 with the bar up-ended and then turning the bar into horizontal position and hooking its outer end to the forwardly extending arm of bellcrank 25, after which spring 36 may be connected to bar 34 and bracket 24. Bellcrank 25 and arm 39 support bar 34 for endwise movement and for fore-and-aft swinging about pivot 25'I with wheel I6 in the plane of slot 42, which slot is slightly wider vertically than the thickness of said wheel.

The operation of the improved back spacing mechanism is as follows:

The several movable parts of the back spacing means for wheels I6 are normally maintained positioned as shown in Figs. 1, 2 and 3 by spring 36. In this normal or idle condition of the back spacing means, the forwardly extending keybearing arm of key lever 29 is pressed upward against stop 33, stop face 42b of bar 34 is retracted rightward from the right hand face of part 39l of arm 39, the rear face of bar 34 is drawn rearward against stop shoulders 40 on arm 39, and the inner or left hand end of bar 34 is retracted out of the path of rotation of the teeth of wheel I 6 in position for projection of the inner end of the bar 34 between two teeth of wheel I6 upon depression of key 30, said teeth located forward of the axis of wheel I6.

Upon depression of key 30, bar 34 will be projected endwise toward the left or toward wheel I6, its inner end entering between two teeth of wheel I6 and its inner end edge engaging behind one tooth at or substantially at the base or root of the tooth and pushing said tooth toward the left until stop edge 42b of bar slot 42 abuts the right hand face of arm 39 to arrest endwise movement of bar 34 by key lever 29. This movement of bar 34, as will be evident from a comparison of Figs. 3 and 4, is sufllcient to carry clockwise (or reversely from letter feed direction) away from dog I5 the tooth of wheel I6 which was engaged with said dog prior to depression of key 30 and to cause the next tooth on the wheel to click past said dog. In event of rapid o r violent depression of the key 30 there may occur a tendency of wheel 8 to continue its reverse rotation beyond that indicated in Fig. 4. Should this occur. the tooth of wheel I8 following that one being pushed by bar 34 will engage stop 42' and cam the bar 34 forward about pivot 25* against stop shoulders ll and jam-lock the wheel I6 (as shown in Fig. 5) before said wheel can turn reversely far enough to permit a second tooth of the wheel I6 to pass dog I5 and also before the tooth engaged with stop 42* can pass said stop. The pivotal connection of bar 3l to bellcrank permits this last described movement of the bar 3l and also permits the inner driving end of said bar to follow around the axis of wheel I6 that tooth which it drives during any depression of key 30. During full depression of key 30, and except during the partial toothspace 'overthrow permitted, spring 36 keeps the driving end of bar 3l down at or close to the root of the tooth being driven, so that bar 34 moves endwise substantially tangentially to the root circle or dedendum circle of toothed wheel I6. Upon release of pressure on key 30, the back spacing mechanism for wheel I8 reassumes normal condition by reason of the tension pull exerted on bar 3l by spring 38.

What I claim is:

1. In a typewriting machine having a platen carriage, and a toothed escapement wheel rotatable in one direction for letter-space feeding of the platen carriage and reversely rotatable to back space the carriage, back spacing mechanism for reversely rotating said wheel step-by-step comprising a wheel driving bar for reversely driving said wheel, means for at will projecting said bar endwise thereof in the plane of said wheel against a tooth of said wheel in a direction to reversely. drive the wheel, stationary means engageable by said bar to limit such endwise projected movement of the bar, said bar having an aperture therein adjacent its wheel driving end adapted to receive the wheel tooth trailing the one driven by the bar, said latter tooth engageable with an edge of said aperture to arrest reverse rotation of the wheel, and stationary means engageable by the bar to prevent said latter tooth forcing itself past said driving end of the bar.

2. In a typewriting machine having a carriage feed mechanism including a toothed escapement wheel, back spacing means comprising a bar having a wheel driving end and a closed longitudinal slot adjacent said end, means mounting said bar for endwise movement toward said wheel and for lateral movement in the plane of said wheel. key actuated means for projecting said bar endwise to engage its wheel driving end between two teeth of said wheel and drive the wheel in back spacing direction through pressure of said end of said bar on one of said two teeth, and stationary means engageable by the bar at one end edge of said slot and by said bar at one face of the bar to limit respectively endwise projection and lateral movement of the bar in the plane of said wheel, the other of said teeth being engageable with the opposite end edge of said slot in said bar to prevent overthrow of the wheel.

3. In a typewriting machine having a carriage feed mechanism including a toothed escapement wheel, back spacing means comprising a bar having a wheel driving end and a closed longitudinal slot adjacent said end, means mounting said bar for endwise movement substantially tangentially to said wheel and for lateral movement in the plane of said wheel, key actuated means for projecting said bar endwise to engage its wheel driving end between two teeth of said wheel and drive the wheel in back spacing direction through pressure of said end of said bar on one of said two teeth, stationary means engageable by the bar at one end edge ofsald slot and by said bar at one face of the bar to limit respectively endwise projection and lateral movement of the bar in the plane of said wheel, the other of said teeth being engageable with the opposite endedge of said slot in said bar to prevent overthrow of the wheel, said stationary means being located intermediate the ends of the bar and adjacent said wheel, and said key-actuated means including a lever to which said bar is pivotally heid at that end of the bar opposite the wheel driving end.

4. In a typewriting machine having a carriage feed mechanism including a toothed escapement wheel rotatable in one direction about an upstanding axis to letter space the carriage during typing and reversely rotatable to back space the carriage, back spacing mechanism for reversely rotating said wheel step-by-step comprising a wheel driving bar supported horizontally in the machine for longitudinal projection of said bar substantially transversely of the machine and substantially tangentially to the root circumference of said wheel to cause the inner end of said bar to enter between two teeth of said wheel and push against one of said teeth adjacent the tooth.

root and reversely drive the wheel, said bar having adjacent its inner end an aperture to receive the second one oi said two teeth, means for at will projecting said bar endwise inward from an idle position in which the inner end of the bar is retracted from the wheel, and means engageable by the bar for blocking movement of the bar in a position in which the second one of said teeth will engage an edge of the bar aperture to block overthrow of the wheel.

5. In a'typewriting machine having a toothed escapement wheel rotatable about an upstanding axis step-by-step in one direction for platen carriage feeding and in the reverse direction for carriage back spacing, back spacing mechanism operable upon said wheel comprising a bellcrank lever supported to one side of said wheel adjacent one side of the machine for oscillation about an upstanding axis and having an arm swingable transversely of the machine and an arm swingable foreand-aft of the machine by oscillation of said lever, key actuated means connected to the secondmentioned leverarm to rock the lever in a direction to swing the rst-mentioned lever arm inward, a substantially horizontally disposed bar for reversely driving said escapement wheel extending substantially transversely of the machine inward from the first-mentioned lever arm toward said wheel and pivotally held at its outer end to said lever arm for swinging of said bar fore-andaft of the machine about said pivotal connection, stationary means between said wheel and lever and adjacent said wheel slidably supporting said bar adjacent its inner end for movement both transversely and fore-and-aft of the machine, a spring connected to said bar to normally urge it endwise outward and swing it rearward to an idle position in which said bar is retracted from the wheel, said stationary means including means for limiting fore-and-ait swinging of said bar in both directions and for directing the inner end of the bar between two teeth of said wheel approximately tangentially to the root circumference of the wheel upon inward projection of said bar by said key actuated means, said bar having adjacent its inner end a longitudinal slot one end of which is abuttable against said stationary means to limit inward projection of said bar and the other end of which is abuttable by a tooth of said wheel to prevent overthrow of the wheel.

6. Back spacing means for the toothed escapement wheel of a typewritlng machine carriage feed mechanism, comprising a wheel driving bar havlng a wheel driving end, a key actuated bellcrank having an arm with a hook end hooked in the other end of said bar, and a fixed guide and stop member for the wheel driving end portion of the bar comprising a ilat arm having a reduced portion intermediate its ends, said bar having adjacent its wheel driving end a longitudinal slot through which the reduced portion of said arm -extends, said bar being connectible to and disconnectible from said arm upon turning of said bar to position the slot to extend edgewise of the arm.

7. In a typewriting machine having a toothed escapement wheel rotative tooth-space by toothspace in opposite directions to respectively letterspace feed a paper carriage in typing and to backspace the carriage, back-spacing means for driving said wheel tooth-space by tooth-space to backspace the carriage comprising a wheel-driving bar normally spring-retracted from said wheel and having a wheel-driving end edge forthrust engagement with a tooth of said wheel and an aperture adjacent said end edge to receive a tooth of said wheel. key-actuated means for driving said bar to turn said wheel for back-spacing, and guiding and arresting means mounted in the machine and engaging the said bar, said means including a stop means to arrest movement of said bar in back spacing direction, to positively conne movement of said bar in wheel-driving direction to a maximum xed path in which said bar will first drive 4said wheel one tooth space in back spacing direction through thrust engagement of said end edge of the bar with one tooth of said wheel and will thereafter be arrested by said stop means and cooperate with said guiding means to positively preventI overthrow of said wheel a second tooth space through engagement of a different tooth of said wheel with a wall of said bar aperture.

JOSEPH P. BARKDOLL. 

